Rhodium complexes of chiral phosphines

ABSTRACT

Novel chiral phosphines are disclosed which when complexed with rhodium provide catalyst compositions for asymmetric hydrogenations.

BACKGROUND OF THE INVENTION

Achiwa in J.A.C.S., 98, 8265 (1976) describes BPPM[(2S,4S)-N-butoxycarbonyl-4-diphenyl-phosphino-2-diphenylphosphinomethyl-pyrrolidine]and the use of this compound in the form of a rhodium complex as acatalyst for asymmetric hydrogenation.

Achiwa in papers in Tetrahedron Letters, No. 50, 4431 (1977) andChemistry Letters, 297-998 (1978) has described the asymmetrichydrogenation of ketopantolactons with a rhodium complex of BPPM.

Finally, Knowles et al. in "Fundamental Research in HomogeneousCatalysis", Vol. III, pages 537-548, particularly page 542, Editor:Tsutsui Publisher, Plenum Press, New York, refers erroneously tophosphines corresponding to formula I herein where R¹ is --SO₂ --CH₃.However, from the content of the text it is clear that the pivaloylgroup was intended.

DESCRIPTION OF THE INVENTION

The present invention is concerned with novel chiral phosphines of thegeneral formula ##STR1## wherein R represents aryl and R¹ represents agroup of the formula ##STR2## in which R² represents aryl, diarylamino,di(lower alkyl)amino, hydroxy, aryloxy or lower alkoxy.

The invention is also concerned with the manufacture of the phosphinesof formula I and their use for asymmetric hydrogenations.

The term "aryl" signifies in the scope of the present invention phenylwhich optionally carries in the para- and/or meta-position lower alkylor lower alkoxy groups, preferably methyl or methoxy groups, or di(loweralkyl)amino groups, preferably dimethylamino groups. Moreover, two arylgroups attached to the same phosphorus atom can be bonded togetherdirectly via the o-position or via a methylene, ethylene or propylenegroup. The term "aryloxy" signifies groups in which the aryl moiety hasthe foregoing significance. The term "lower alkyl" signifies in thescope of the present invention straight-chain and branched-chain alkylgroups containing 1 to 7 carbon atoms such as, for example, methyl,ethyl, propyl, isopropyl, n-butyl, isobutyl, tert.butyl and the like.The term "lower alkoxy" signifies groups in which the alkyl moiety hasthe foregoing significance. Furthermore, the notation " " signifies thatthe corresponding group is situated above the plane of the molecule,while the notation " " signifies that the corresponding group issituated below the plane of the molecule.

Preferred phosphines of formula I are those in which R representsphenyl, p-tolyl, m-tolyl or 3,5-xylyl and R² in the groups R¹ representsphenyl, p-tolyl, m-tolyl, phenoxy or di(lower alkyl)amino. Especiallypreferred phosphines are, moreover, those in which R¹ represents thegroup ##STR3## The following are examples of preferred compounds offormula I:(2S,4S(-4-(Diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(diphenylphosphinyl)-pyrrolidine;

(2S,4S)-4-(di-p-tolylphosphino)-2-[(di-p-tolylphosphino)methyl]-1-(diphenylphosphinyl)-pyrrolidine;

(2S,4S)-4-(di-m-tolylphosphino)-2-[(di-m-tolylphosphino)methyl]-1-(diphenylphosphinyl)pyrrolidine;

(2S,4S)-4-(di-3,5-xylylphosphino)-2-[(di-3,5-xylylphosphino)methyl]-1-(diphenylphosphinyl)-pyrrolidine;

(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-[di-p-tolylphosphinyl)-pyrrolidine;

(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(di-m-tolylphosphinyl)-pyrrolidine;

diphenyl[(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-pyrrolidinyl]-phosphonate;

diphenyl[(2S,4S)-4-(di-p-tolylphosphino)-2-[(di-p-tolylphosphino)methyl]-1-pyrrolidinyl]-phosphonate;

diphenyl[(2S,4S)-4-(di-m-tolylphosphino)-2-[(di-m-tolylphosphino)methyl]-1-pyrrolidinyl]-phosphonate;

[(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-pyrrolidinyl]-N,N,N',N'-tetramethylphosphonicacid diamide;

[(2S,4S)-4-(di-p-tolylphosphino)-2-[(di-p-tolylphosphino)methyl]-1-pyrrolidinyl]-N,N,N',N'-tetramethylphosphonicacid diamide;

[(2S,4S)-4-(di-m-tolylphosphino)-2-[(di-m-tolylphosphino)methyl]-1-pyrrolidinyl]-N,N,N',N'-tetramethylphosphonicacid diamide;

[(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-pyrrolidinyl]-diphenylphosphine;

(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(p-tolylsulphonyl)-pyrrolidine;

(2S,4S)-4-(di-p-tolylphosphino)-2-[(di-p-tolylphosphino)methyl]-1-(p-tolylsulphonyl)-pyrrolidine;

(2S,4S)-4-(di-m-tolylphosphino)-2-[(di-m-tolylphosphino)methyl]-1-(p-tolylsulphonyl)-pyrrolidine;

phenyl(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-pyrrolidinesulphonate;

phenyl(2S,4S)-4-(di-p-tolylphosphino)-2-[(di-p-tolylphosphino)methyl]-1-pyrrolidinesulphonate;

phenyl(2S,4S)-4-(di-m-tolylphosphino)-2-[(di-m-tolylphosphino)methyl]-1-pyrrolidinesulphonate;

(2S,4S)-4-diphenylphosphino)-2-[diphenylphosphino)methyl]-N,N-dimethyl-1-pyrrolidinesulphonamide;

(2S,4S)-4-(di-p-tolylphosphino)-2-[(di-p-tolylphosphino)methyl]-N,N-dimethyl-1-pyrrolidinesulphonamide;

(2S,4S)-4-(di-m-tolylphosphino)-2-[(di-m-tolylphosphino)methyl]-N,N-dimethyl-1-pyrrolidinesulphonamide;

(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-pyrrolidinesulphonicacid;

[(2S,4S)-2-(5H-dibenzophosphol-5-ylmethyl)-4-(5H-dibenzophosphol-5-yl)-1-pyrrolidinyl]diphenylphosphineoxide;

5-[(2S,4S)-2-[(diphenylphosphino)methyl]-4-(diphenylphosphino)-1-pyrrolidinyl]-5H-dibenzophosphol5-oxide;

[(2S,4S)-2-[5(10H)-acridophosphinylmethyl]-4-(5(10H)-acridophosphinyl]-1-pyrrolidinyl]diphenylphosphineoxide;

5[(2S,4S)-2-[(diphenylsphosphino)methyl]-4-(diphenylphosphino)-1-pyrrolidinyl]-5,10-dihydroacridophosphine5 oxide;

5-[(2S,4S)-2-(5H-dibenzophosphol-5-ylmethyl)-4-(5H-dibenzophosphol-5-yl)-1-pyrrolidinyl]-5H-dibenzophosphol5 oxide; and

[(2S,4S)-2-[(diphenylphosphino)methyl]-4-(diphenylphosphino)-1-pyrrolidinyl]diphenylphosphinesulphide.

The compounds of formula I provided by the invention can be manufacturedby

(a) reacting a compound of the general formula ##STR4## wherein R hasthe significance given earlier, with a compound of the general formula##STR5## wherein R² has the significance given earlier and R³ representschlorine or fluorine,

or

(b) reacting a compound of the general formula ##STR6## wherein R¹ hasthe significance given earlier and R⁴ represents aryl or lower alkyl,with a compound of the general formula ##STR7## wherein R has thesignificance given earlier and R⁵ represents lithium, sodium, potassiumor magnesium halide.

The reaction of the compounds of formula II with the compounds offormulae IIIa-IIIe can be carried out in a manner known per se, wherebyit must be carried out with the strict exclusion of oxygen, namely underan inert gas atmosphere (e.g. under nitrogen, argon and the like). Thereaction can conveniently be carried out in an inert organic solventsuch as an aromatic hydrocarbon (e.g. benzene, toluene and the like) oran ether (e.g. diethyl ether, tetrahydrofuran, dioxan and the like) and,if necessary, with the addition of a tertiary amine. The temperature andthe pressure at which this reaction is carried out are not critical andaccordingly the reaction can be carried out readily at about roomtemperature and atmospheric pressure.

The compounds of formulae II and IIIa-IIIe used as starting materialsare known compounds or analogues of known compounds which can beprepared readily in an analogous manner to the preparation of the knowncompounds.

The reaction of the compounds of formula IV with the compounds offormula V can be carried out in a manner known per se, whereby it mustbe carried out with the strict exclusion of oxygen, namely under aninert gas atmosphere (e.g. under nitrogen, argon and the like). Thereaction is conveniently carried out in an inert organic solvent such asan ether (e.g. tetrahydrofuran, dioxan, diethyl ether and the like), ifdesired in the presence of a hydrocarbon (e.g. hexane, benzene, tolueneand the like). The reaction is conveniently carried out at a temperatureof about -15° C. to about room temperature, preferably at about -10° C.to about 0° C. The pressure at which the reaction is carried out is notcritical and accordingly the reaction can be carried out readily atatmospheric pressure.

The compounds of formula IV used as starting materials are novelcompounds and are likewise an object of the present invention. They can,however, be prepared in a manner known per se; for example, inaccordance with Reaction Schemes I and II hereinafter. In these ReactionSchemes Ts signifies the tosyl group and A signifies the group ##STR8##

The compounds of formula V used as starting materials are known or areanalogues of known compounds which can be prepared readily in a manneranalogous to the preparation of the known compounds.

The phosphines of formula I provided by the invention form complexeswith rhodium which can be used as catalysts in asymmetrichydrogenations. These catalysts, i.e. the complexes of rhodium and thephosphines of formula I, are novel and are also an object of the presentinvention. These catalysts can be manufactured in a manner which issimple and known per se; for example, by reacting a compound of formulaI with a compound yielding rhodium in a suitable inert organic solvent.Suitable compounds yielding rhodium are, for example, rhodiumtrichloride hydrate, rhodium tribromide hydrate, rhodium sulphate ororganic rhodium complexes with ethylene, propylene and the like as wellas with bis-olefins such as 1,5-cyclooctadiene, 1,5-hexadiene,bicyclo-2,2,1-hepta-2,5-diene or with other dienes which form readilysoluble complexes with rhodium. Preferred compounds yielding rhodium areu,u'-dichloro-bis-[bis-(olefin)-rhodium (I)], for exampleu,u'-dichloro-bis-[(1,5-cyclooctadiene-rhodium (I)] oru,u'-dichloro-bis-[(norbornadiene)-rhodium (I)].

As mentioned earlier, the phosphines provided by the invention serve asligands in rhodium complexes which are used as catalysts in asymmetrichydrogenations. They are especially interesting in connection with theasymmetric hydrogenation of α-keto-carboxylic acid esters to thecorresponding α-hydroxy-carboxylic acid esters and especially ofdihydro-4,4-dimethyl-2,3-furandione (ketopantolactone) to thecorresponding R-(α-hydroxy-β,β-dimethyl-γ-butyrolactone)[R-(-)-pantolactone].

In carrying out the aforementioned asymmetric hydrogenations, thephosphines of formula I can be brought into contact such as, in asolution of an asymmetric compound to be hydrogenated, with a compoundyielding rhodium. On the other hand, the phosphines of formula I can bereacted firstly in a suitable solvent with a compound yielding rhodiumto give the corresponding catalyst complex and this can then be added toa solution of an asymmetric compound to be hydrogenated.

Not only the reaction of the phosphines of formula I with the compoundyielding rhodium but also the aforementioned asymmetric hydrogenationscan be carried out in suitable organic solvents which are inert underthe reaction conditions. Especially suitable organic solvents are loweralkanols such as, for example, methanol or ethanol, aromatichydrocarbons such as benzene or toluene, cyclic ethers such astetrahydrofuran or dioxan, esters such as, for example, ethyl acetate ormixtures thereof and the like. The ratio between rhodium and the ligandsof formula I conveniently lies between about 0.05 and about 5 mol,preferably between about 0.5 and about 2 mol, of rhodium per mol ofligand of formula I. The ratio between rhodium in the complexes with theligands of formula I and the compounds to be hydrogenated convenientlylies between about 0.00001 and about 5 wt.%, preferably between about0.001 and about 0.5 wt%.

The asymmetric hydrogenations using rhodium complexes with the ligandsof formula I can conveniently be carried out at temperatures of about20° C. to about 100° C., preferably from about 40° C. to about 90° C.These hydrogenations are conveniently carried out under pressure,especially under a pressure of about 1 to about 100 bar, preferably 2 to50 bar.

The following Examples illustrate the present invention:

EXAMPLE 1

1.01 g (2.23 mmol) of(2S,4S)-4-diphenylphosphino-2-diphenylphosphinomethylpyrrolidine, 1.46ml (13.38 mmol) of N-methylmorpholine and 30 ml of toluene were placedin a 500 ml sulphonation flask which was provided with a stirrer,thermometer, dropping funnel and argon gasification. While stirringthere was then added dropwise thereto at room temperature within 10minutes a solution of 0.79 g (3.35 mmol) of diphenylphosphinyl chloridein 10 ml of toluene. The reaction was finished after 7 hours. Themixture was then filtered through a sintered glass suction filter andthe filtrate was evaporated on a rotary evaporator at 60° C./17 mbar.The residue (2.2 g) was taken up in 30 ml of diethyl ether and treatedwith 30 ml of 3N hydrochloric acid. The ether phase was then separatedand the aqueous phase was extracted a further twice with 30 ml ofdiethyl ether each time. The extracts were dried over sodium sulphate,filtered off and concentrated on a rotary evaporator at 60° C./17 mbar.For purification the residue (1.57 g) was chromatographed over 140 g ofKieselgel 60 (0.063 to 0.20 mm granular size). A mixture ofbenzene/ethyl acetate/ethanol (8:2:1) was used as the eluant. Afterevaporation of the solvent and drying for 16 hours/1 mbar, there wasobtained 1.12 g (76.8%) of pure(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(diphenylphosphinyl)-pyrrolidine.Melting point: sintering from 65° C., clear melting at 130° C. [α]_(D)²⁰ =-21.4° (c=0.5 in benzene).

The following compounds are manufactured in an analogous manner:

(2S,4S)-4-(Di-p-tolylphosphino)-2-[(di-p-tolylphosphino)methyl]-1-(diphenylphosphinyl)-pyrrolidine,[α]_(D) ²⁰ =-33.2° (c=0.5 in benzene);

(2S,4S)-4-(di-m-tolylphosphino)-2-[(di-m-tolylphosphino)methyl]-1-(diphenylphosphinyl)-pyrrolidine,[α]_(D) ²⁰ =-25.8° (c=0.6 in benzene);

(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(di-p-tolylphosphinyl)-pyrrolidine,[α]_(D) ²⁰ =-13.8° (c=0.5 in benzene);

(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(di-m-tolylphosphinyl)-pyrrolidine,[α]_(D) ²⁰ =-21.3° (c=0.6 in benzene);

[(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-pyrrolidinyl]-diphenylphosphine,[α]_(D) ²⁰ =-64.0° (c=0.6 in benzene);

diphenyl[(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-pyrrolidinyl]-phosphonate,[α]_(D) ²⁰ =-63.3° (c=0.6 in benzene); and

[(2S,4S)-4-diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-pyrrolidino]-N,N,N',N'-tetramethylphosphonicacid diamide, [α]_(D) ²⁰ =-60.7° (c=0.6 in benzene).

EXAMPLE 2

7.5 g (38 mmol) of diphenylphosphine were dissolved in 25 ml oftetrahydrofuran in a 200 ml sulphonation flask, provided with a stirrer,thermometer, two dropping funnels, argon gasification and cooling bath,and the solution was cooled to 0° C. Thereupon, 28 ml of a 1.5M n-butyllithium solution (hexane; 42 mmol) were added dropwise within 15 minutesat 0°-5° C. while stirring, the initially colourless solution becomingintensively orange-red in colour. A solution of 9.7 g (16.7 mmol) of(2S,4R)-1-(p-tolylsulphonyl)-4-[(p-tolylsulphonyl)oxy]-2-pyrrolidinylmethylp-toluenesulphonate in 50 ml of tetrahydrofuran was then added dropwiseat -5° C. within 30 minutes, the solution becoming pale orange incolour. After a reaction time of 5 hours at 0° C., a few drops of waterwere added and the solution was then evaporated on a rotary evaporatorat 60° C./17 mbar. The residue was dissolved in 100 ml of benzene,washed three times with 100 ml of water each time and the aqueous phaseswere back-washed with 100 ml of benzene. The combined benzene extractswere evaporated on a rotary evaporator at 60° C./17 mbar. The productobtained (15.2 g of yellowish oil), which crystallizes partially uponstanding, was, for purification, dissolved in benzene and the solutionwas filtered over 240 g of Kieselgel 60 (0.63-0.20 mm granular size).After evaporation of the solvent and drying for 16 hours at 40° C./17mbar, there were obtained 6.5 g (63.9%) of(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(p-tolylsulphonyl)-pyrrolidineas a colourless foam. [α]_(D) ²⁰ =-125.8° (c=1 in benzene).

The(2S,4R)-1-(p-tolylsulphonyl)-4-[(p-tolylsulphonyl)oxy]-2-pyrrolidinylmethylp-toluenesulphonate used as the starting material can be prepared asfollows:

35.6 g (0.27 mol) of (2S,4R)-4-hydroxyproline were dissolved in 300 ml(0.60 mol) of 2N sodium hydroxide in a 750 ml sulphonation flask whichwas provided with stirrer, dropping funnel, thermometer and condenser.Thereupon, within 10 minutes there was added dropwise thereto a solutionof 63 g (0.33 mol) of p-toluenesulphonyl chloride in 180 ml of diethylether. The temperature was held at 16°-20° C. by means of a water bath.After intensive stirring at room temperature for 16 hours, the reactionhas finished. The aqueous phase (pH about 7) was separated andback-washed with 250 ml of diethyl ether. The ether phases wereback-washed a further twice with 100 ml of deionized water each time.The combined aqueous phases were acidified to pH 2 with 25 ml ofconcentrated hydrochloric acid (27%) while cooling with ice at 5° C. andstirred for 1.5 hours at 5° C. The separated crystals were filtered offunder suction, washed with 1 liter of deionized water and dried for 16hours in a vacuum drying oven at 40° C./17 mbar. The resulting product(76.2 g of white crystals of melting point (142°-145° C.) was, forpurification, dissolved in 200 ml of hot ethanol/water (1:4, v/v) andrecrystallized while stirring and slowly cooling to 5° C. The whitecrystals obtained after drying (73.4 g) were again recrystallized from150 ml of ethanol/water (1:4, v/v) as previously described and dried ina vacuum drying oven at 50° C./17 mbar. There were obtained 69.4 g(89.6%) of(2S,4R)-4-hydroxy-1-(p-tolylsulphonyl)-2-pyrrolidinecarboxylic acid ofmelting point 146°-147° C. [α]_(D) ²⁰ =-87.6° (c=1 in ethanol).

57 g (0.20 mol) of(2S,4R)-4-hydroxy-1-(p-tolylsulphonyl)-2-pyrrolidinecarboxylic acid weredissolved in 300 ml of tetrahydrofuran in a 1.5 l sulphonation flaskwhich was provided with a stirrer, thermometer, dropping funnel,condenser with an acetone washing flask connected at the outlet side andargon gasification. 500 ml of 1M diborane solution (tetrahydrofuran;0.50 mol) were then added dropwise while stirring at 5°-10° C. within1.2 hours. The reaction mixture was stirred at room temperatureovernight. Thereupon, the mixture was decomposed by the slow dropwiseaddition of 50 ml of deionized water at 0°-5° C. (exothermic reaction)and subsequently evaporated on a rotary evaporator at 50° C./17 mbar.The residue was taken up in 150 ml of deionized water and extracted sixtimes with 300 ml of ethyl acetate each time. The extracts were washedthree times with 150 ml of saturated sodium chloride solution each time,dried over sodium sulphate and evaporated on a rotary evaporator at 50°C./17 mbar. For purification, the residue obtained was recrystallizedfrom 100 ml of ethyl acetate. The crystals obtained were filtered offunder suction and dried in a drying oven at 40° C./17 mbar. There werethus obtained 34 g (62.7%) of(2S,4R)-4-hydroxy-1-(p-tolylsulphonyl)-2-pyrrolidinemethanol of meltingpoint 133°-134° C.; [α]_(D) ²⁰ =-47.4° (c=1 in ethanol).

6.8 g (0.025 mol) of(2S,4R)-4-hydroxy-1-(p-tolylsulphonyl)-2-pyrrolidinemethanol weredissolved in 20 ml of pyridine in a 200 ml sulphonation flask, providedwith a stirrer, thermometer, dropping funnel, argon gasification and icebath, and the solution was cooled to 0° C. Within 45 minutes there wasadded dropwise at 0°-3° C. while stirring a solution of 12 g (0.063 mol)of p-toluenesulphonyl chloride in 20 ml of pyridine. Pyridinehydrochloride begins to precipitate out after about 1 hour. The mixturewas stirred at room temperature overnight and then 100 ml of deionizedwater were cautiously added dropwise at 0°-10° C. (strong exothermicreaction), a white crystal slurry separating. After stirring in an icebath for 3 hours, the crystals was filtered off under suction, washedfive times with 40 ml of cold deionized water each time and dried for 2hours in a drying oven at 60° C./17 mbar. For purification, the productobtained was recrystallized from 50 ml of ethyl acetate. The separatedcrystals were filtered off under suction and dried in a drying oven at40° C./17 mbar. There were obtained 9.8 g (67.6%) of(2S,4R)-1-(p-tolylsulphonyl)-4-[(p-tolylsulphonyl)oxy]-2-pyrrolidinylmethyl-p-toluenesulphonateof melting point 131°-134° C.; [α]_(D) ²⁰ =-77.2° (c=1 in benzene).

EXAMPLE 3

50 g (0.39 mol) of dihydro-4,4-dimethyl-2,3-furandione and 300 ml oftoluene were placed in a 1 liter stirring steel autoclave. In order toremove the air from the system, the autoclave was evacuated five timeswith a high vacuum pump and in each case gassed with 10 bar of hydrogen.The autoclave, heated to 40° C., was thereupon again evacuated. Then,the yellow catalyst solution, prepared from 0.029 g (0.063 mmol) ofchloronorbornadiene-rhodium (I) dimer and 0.082 g (0.126 mmol) of(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(diphenylphosphinyl)pyrrolidinein 50 ml of toluene, was introduced and then the autoclave was gassedwith 40 bar of hydrogen. The hydrogenation was carried out withintensive stirring at 40° C. and a constant hydrogen pressure of 40 barand was finished after 20 hours. The pale yellow solution was thenrinsed from the autoclave with toluene and the solvent was removed byevaporation on a rotary evaporator at 60° C./17 mbar. The residue (54.7g) was distilled at 130°-150° C. (bath temperature) and 0.05 mbar. Therewere obtained 50.2 g (98.9%) of crudeR-(α-hydroxy-β,β-dimethyl-γ-butyrolactone) with an optical purity of84.3%; [α]_(D) ²⁰ =-43.1° (c=1 in water).

EXAMPLE 4

50 g (0.39 mol) of dihydro-4,4-dimethyl-2,3-furandione and 300 ml ofethyl acetate were placed in a 1 liter stirring steel autoclave. Inorder to remove the air from the system, the autoclave was evacuatedfive times with a high vacuum pump and in each case gassed with 10 barof hydrogen. The autoclave, heated to 40° C., was thereupon againevacuated. Then, the yellow catalyst solution, prepared from 0.029 g(0.063 mmol) of chloronorbornadiene-rhodium (I) dimer and 0.076 g (0.126mmol) of(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(p-tolylsulphonyl)-pyrrolidinein 50 ml of ethyl acetate, was introduced and then the autoclave wasgassed with 40 bar of hydrogen. The hydrogenation was carried out withintensive stirring at 60° C. and a constant hydrogen pressure of 40 barand was finished after 8 hours. The pale yellow solution was then rinsedfrom the autoclave with ethyl acetate and the solvent was removed byevaporation on a rotary evaporator at 60° C./17 mbar. The residue (59.9g) was distilled at 130°-150° C. (bath temperature) and 0.05 mbar. Therewere obtained 50.6 g (99.8%) of crudeR-(α-hydroxy-β,β-dimethyl-γ-butyrolactone) with an optical purity of81.8%; [α]_(D) ²⁰ =-41.7° (c=1 in water).

We claim:
 1. A rhodium complex with a chiral phosphine of the formula##STR9## wherein R represents aryl and R¹ represents a group of theformula ##STR10## in which R² represents aryl, di(lower alkyl)amino,hydroxy, aryloxy or lower alkoxy.
 2. Complexes in accordance with claim1 wherein R¹ represents a group of the formula ##STR11##
 3. Complexes inaccordance with claim 2 wherein R represents phenyl, p-tolyl or m-tolyland R² in the group R¹ represents phenyl, p-tolyl or m-tolyl.
 4. Thecomplex in accordance with claim 3, wherein the compound of formula I is(2S,4S)-4-diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(diphenylphosphinyl)-pyrrolidine.5. The complex in accordance with claim 3, wherein the compound offormula I is(2S,4S)-4-(di-p-tolylphosphino)-2-[(di-p-tolylphosphino)methyl]-1-diphenylphosphinyl)-pyrrolidine.6. The complex in accordance with claim 3, wherein the compound offormula I is(2S,4S)-4-di-m-tolylphosphino)-2-[(di-m-tolylphosphino)methyl]-1-(diphenylphosphinyl)-pyrrolidine.7. The complex in accordance with claim 3, wherein the compound offormula I is(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(di-p-tolylphosphinyl)-pyrrolidine.8. The complex in accordance with claim 3, wherein the compound offormula I is(2S,4S)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]-1-(di-m-tolylphosphinyl)-pyrrolidine.